1
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Mazzaferro S, Kang G, Natarajan K, Hibbs RE, Sine SM. Structural bases for stoichiometry-selective calcium potentiation of a neuronal nicotinic receptor. Br J Pharmacol 2024; 181:1973-1992. [PMID: 38454578 DOI: 10.1111/bph.16321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Revised: 01/05/2024] [Accepted: 01/08/2024] [Indexed: 03/09/2024] Open
Abstract
BACKGROUND AND PURPOSE α4β2 nicotinic acetylcholine (nACh) receptors assemble in two stoichiometric forms, one of which is potentiated by calcium. The sites of calcium binding that underpin potentiation are not known. EXPERIMENTAL APPROACH To identify calcium binding sites, we applied cryo-electron microscopy (cryo-EM) and molecular dynamics (MD) simulations to each stoichiometric form of the α4β2 nACh receptor in the presence of calcium ions. To test whether the identified calcium sites are linked to potentiation, we generated mutants of anionic residues at the sites, expressed wild type and mutant receptors in clonal mammalian fibroblasts, and recorded ACh-elicited single-channel currents with or without calcium. KEY RESULTS Both cryo-EM and MD simulations show calcium bound to a site between the extracellular and transmembrane domains of each α4 subunit (ECD-TMD site). Substituting alanine for anionic residues at the ECD-TMD site abolishes stoichiometry-selective calcium potentiation, as monitored by single-channel patch clamp electrophysiology. Additionally, MD simulation reveals calcium association at subunit interfaces within the extracellular domain. Substituting alanine for anionic residues at the ECD sites reduces or abolishes stoichiometry-selective calcium potentiation. CONCLUSIONS AND IMPLICATIONS Stoichiometry-selective calcium potentiation of the α4β2 nACh receptor is achieved by calcium association with topographically distinct sites framed by anionic residues within the α4 subunit and between the α4 and β2 subunits. Stoichiometry-selective calcium potentiation could result from the greater number of calcium sites in the stoichiometric form with three rather than two α4 subunits. The results are relevant to modulation of signalling via α4β2 nACh receptors in physiological and pathophysiological conditions.
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Affiliation(s)
- Simone Mazzaferro
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
- Wellcome Trust - Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge, UK
- Wellcome Trust - Medical Research Council Cambridge Stem Cell Institute, University of Cambridge, Cambridge, UK
| | - Guipeun Kang
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Kathiresan Natarajan
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
| | - Ryan E Hibbs
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Neurobiology, University of California San Diego, La Jolla, California, USA
| | - Steven M Sine
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, Minnesota, USA
- Department of Neurology, Mayo Clinic College of Medicine and Science, Rochester, Minnesota, USA
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2
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Patel DC, Swift N, Tewari BP, Browning JL, Prim C, Chaunsali L, Kimbrough IF, Olsen ML, Sontheimer H. Increased expression of chondroitin sulfate proteoglycans in dentate gyrus and amygdala causes postinfectious seizures. Brain 2024; 147:1856-1870. [PMID: 38146224 PMCID: PMC11068111 DOI: 10.1093/brain/awad430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Revised: 10/05/2023] [Accepted: 12/08/2023] [Indexed: 12/27/2023] Open
Abstract
Alterations in the extracellular matrix are common in patients with epilepsy and animal models of epilepsy, yet whether they are the cause or consequence of seizures and epilepsy development is unknown. Using Theiler's murine encephalomyelitis virus (TMEV) infection-induced model of acquired epilepsy, we found de novo expression of chondroitin sulfate proteoglycans (CSPGs), a major extracellular matrix component, in dentate gyrus (DG) and amygdala exclusively in mice with acute seizures. Preventing the synthesis of CSPGs specifically in DG and amygdala by deletion of the major CSPG aggrecan reduced seizure burden. Patch-clamp recordings from dentate granule cells revealed enhanced intrinsic and synaptic excitability in seizing mice that was significantly ameliorated by aggrecan deletion. In situ experiments suggested that dentate granule cell hyperexcitability results from negatively charged CSPGs increasing stationary cations on the membrane, thereby depolarizing neurons, increasing their intrinsic and synaptic excitability. These results show increased expression of CSPGs in the DG and amygdala as one of the causal factors for TMEV-induced acute seizures. We also show identical changes in CSPGs in pilocarpine-induced epilepsy, suggesting that enhanced CSPGs in the DG and amygdala may be a common ictogenic factor and potential therapeutic target.
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Affiliation(s)
- Dipan C Patel
- Department of Neuroscience, School of Medicine, University of Virginia, Charlottesville, VA 22903, USA
| | - Nathaniel Swift
- School of Neuroscience, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
| | - Bhanu P Tewari
- Department of Neuroscience, School of Medicine, University of Virginia, Charlottesville, VA 22903, USA
| | - Jack L Browning
- School of Neuroscience, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
| | - Courtney Prim
- Department of Neuroscience, School of Medicine, University of Virginia, Charlottesville, VA 22903, USA
| | - Lata Chaunsali
- Department of Neuroscience, School of Medicine, University of Virginia, Charlottesville, VA 22903, USA
| | - Ian F Kimbrough
- Department of Neuroscience, School of Medicine, University of Virginia, Charlottesville, VA 22903, USA
| | - Michelle L Olsen
- School of Neuroscience, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
| | - Harald Sontheimer
- Department of Neuroscience, School of Medicine, University of Virginia, Charlottesville, VA 22903, USA
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3
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Pawar A, Pardasani KR. Modelling Cross Talk in the Spatiotemporal System Dynamics of Calcium, IP 3 and Nitric Oxide in Neuron Cells. Cell Biochem Biophys 2024:10.1007/s12013-024-01229-5. [PMID: 38376737 DOI: 10.1007/s12013-024-01229-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Accepted: 02/05/2024] [Indexed: 02/21/2024]
Abstract
The bioenergetic system of calcium ([Ca2+]), inositol 1, 4, 5-trisphophate (IP3) and nitric oxide (NO) regulate the diverse mechanisms in neurons. The dysregulation in any or all of the calcium, IP3 and nitric oxide dynamics may cause neurotoxicity and cell death. Few studies are noted in the literature on the interactions of two systems like [Ca2+] with IP3 and [Ca2+] with nitric oxide in neuron cells, which gives limited insights into regulatory and dysregulatory processes in neuron cells. But, no study is available on the cross talk in dynamics of three systems [Ca2+], IP3 and NO in neurons. Thus, the cross talk in the system dynamics of [Ca2+], IP3 and NO regulation processes in neurons have been studied using mathematical model. The two-way feedback process between [Ca2+] and IP3 and two-way feedback process between [Ca2+] and NO through cyclic guanosine monophosphate (cGMP) with plasmalemmal [Ca2+]-ATPase (PMCA) have been incorporated in the proposed model. This coupling handles the indirect two-way feedback process between IP3 and nitric oxide in neuronal cells automatically. The numerical outcomes were acquired by employing the finite element method (FEM) with the Crank-Nicholson scheme (CNS). The present model incorporating the sodium-calcium exchanger (NCX) and voltage-gated calcium channel (VGCC) provides novel insights into the various regulatory and dysregulatory processes due to buffer, IP3-receptor, ryanodine receptor, cGMP kinetics through PMCA channel, etc. and their impacts on the interactive spatiotemporal system dynamics of [Ca2+], IP3 and NO in neurons. It is concluded that the behavior of different crucial mechanisms is quite different for interactions of two systems of [Ca2+] and NO and the interactions of three systems of [Ca2+], IP3 and nitric oxide in neuronal cell due to mutual regulatory adjustments. The association of several neurological disorders with the alterations in calcium, IP3 and NO has been explored in neurons.
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Affiliation(s)
- Anand Pawar
- Department of Mathematics, Bioinformatics and Computer Applications, Maulana Azad National Institute of Technology, Bhopal, 462003, Madhya Pradesh, India.
| | - Kamal Raj Pardasani
- Department of Mathematics, Bioinformatics and Computer Applications, Maulana Azad National Institute of Technology, Bhopal, 462003, Madhya Pradesh, India.
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4
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Pawar A, Pardasani KR. Study of disorders in regulatory spatiotemporal neurodynamics of calcium and nitric oxide. Cogn Neurodyn 2023; 17:1661-1682. [PMID: 37974582 PMCID: PMC10640555 DOI: 10.1007/s11571-022-09902-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 09/26/2022] [Accepted: 10/14/2022] [Indexed: 11/10/2022] Open
Abstract
Experimental studies have reported the dependence of nitric oxide (NO) on the regulation of neuronal calcium ([Ca2+]) dynamics in neurons. But, there is no model available to estimate the disorders caused by various parameters in their regulatory dynamics leading to various neuronal disorders. A mathematical model to analyze the impacts due to alterations in various parameters like buffer, ryanodine receptor, serca pump, source influx, etc. leading to regulation and dysregulation of the spatiotemporal calcium and NO dynamics in neuron cells is constructed using a system of reaction-diffusion equations. The numerical simulation is performed with the finite element approach. The disturbances in the different constitutive processes of [Ca2+] and nitric oxide including source influx, buffer mechanism, ryanodine receptor, serca pump, IP3 receptor, etc. can be responsible for the dysregulation in the [Ca2+] and NO dynamics in neurons. Also, the results reveal novel information about the magnitude and intensity of disorders in response to a range of alterations in various parameters of this neuronal dynamics, which can cause dysregulation leading to neuronal diseases like Parkinson's, cerebral ischemia, trauma, etc.
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Affiliation(s)
- Anand Pawar
- Department of Mathematics, Bioinformatics and Computer Applications, Maulana Azad National Institute of Technology, Bhopal, Madhya Pradesh 462003 India
| | - Kamal Raj Pardasani
- Department of Mathematics, Bioinformatics and Computer Applications, Maulana Azad National Institute of Technology, Bhopal, Madhya Pradesh 462003 India
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5
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Sharma B, Koren DT, Ghosh S. Nitric oxide modulates NMDA receptor through a negative feedback mechanism and regulates the dynamical behavior of neuronal postsynaptic components. Biophys Chem 2023; 303:107114. [PMID: 37832215 DOI: 10.1016/j.bpc.2023.107114] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Revised: 09/22/2023] [Accepted: 09/24/2023] [Indexed: 10/15/2023]
Abstract
Nitric oxide (NO) is known to be an important regulator of neurological processes in the central nervous system which acts directly on the presynaptic neuron and enhances the release of neurotransmitters like glutamate into the synaptic cleft. Calcium influx activates a cascade of biochemical reactions to influence the production of nitric oxide in the postsynaptic neuron. This has been modeled in the present work as a system of ordinary differential equations, to explore the dynamics of the interacting components and predict the dynamical behavior of the postsynaptic neuron. It has been hypothesized that nitric oxide modulates the NMDA receptor via a feedback mechanism and regulates the dynamic behavior of postsynaptic components. Results obtained by numerical analyses indicate that the biochemical system is stimulus-dependent and shows oscillations of calcium and other components within a limited range of concentration. Some of the parameters such as stimulus strength, extracellular calcium concentration, and rate of nitric oxide feedback are crucial for the dynamics of the components in the postsynaptic neuron.
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Affiliation(s)
- Bhanu Sharma
- Department of Biophysics, University of Delhi South Campus, New Delhi 110021, India
| | | | - Subhendu Ghosh
- Department of Biophysics, University of Delhi South Campus, New Delhi 110021, India.
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6
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Zhang P, Maruoka M, Suzuki R, Katani H, Dou Y, Packwood DM, Kosako H, Tanaka M, Suzuki J. Extracellular calcium functions as a molecular glue for transmembrane helices to activate the scramblase Xkr4. Nat Commun 2023; 14:5592. [PMID: 37696806 PMCID: PMC10495444 DOI: 10.1038/s41467-023-40934-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Accepted: 08/11/2023] [Indexed: 09/13/2023] Open
Abstract
The "eat me" signal, phosphatidylserine is exposed on the surface of dying cells by phospholipid scrambling. Previously, we showed that the Xkr family protein Xkr4 is activated by caspase-mediated cleavage and binding of the XRCC4 fragment. Here, we show that extracellular calcium is an additional factor needed to activate Xkr4. The constitutively active mutant of Xkr4 is found to induce phospholipid scrambling in an extracellular, but not intracellular, calcium-dependent manner. Importantly, other Xkr family members also require extracellular calcium for activation. Alanine scanning shows that D123 and D127 of TM1 and E310 of TM3 coordinate calcium binding. Moreover, lysine scanning demonstrates that the E310K mutation-mediated salt bridge between TM1 and TM3 bypasses the requirement of calcium. Cysteine scanning proves that disulfide bond formation between TM1 and TM3 also activates phospholipid scrambling without calcium. Collectively, this study shows that extracellular calcium functions as a molecular glue for TM1 and TM3 of Xkr proteins for activation, thus demonstrating a regulatory mechanism for multi-transmembrane region-containing proteins.
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Affiliation(s)
- Panpan Zhang
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Yoshida-Honmachi, Sakyoku, Kyoto, 606-8501, Japan
- Graduate School of Biostudies, Kyoto University, Konoe-cho, Yoshida, Sakyoku, Kyoto, 606-8501, Japan
| | - Masahiro Maruoka
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Yoshida-Honmachi, Sakyoku, Kyoto, 606-8501, Japan
- Center for Integrated Biosystems, Institute for Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Ryo Suzuki
- Center for Integrative Medicine and Physics (CiMPhy), Institute for Advanced Study, Kyoto University, Yoshida-Honmachi, Sakyoku, Kyoto, 606-8501, Japan
| | - Hikaru Katani
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Yoshida-Honmachi, Sakyoku, Kyoto, 606-8501, Japan
| | - Yu Dou
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Yoshida-Honmachi, Sakyoku, Kyoto, 606-8501, Japan
- Graduate School of Biostudies, Kyoto University, Konoe-cho, Yoshida, Sakyoku, Kyoto, 606-8501, Japan
| | - Daniel M Packwood
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Yoshida-Honmachi, Sakyoku, Kyoto, 606-8501, Japan
| | - Hidetaka Kosako
- Fujii Memorial Institute of Medical Sciences, Institute of Advanced Medical Sciences, Tokushima University, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Motomu Tanaka
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Yoshida-Honmachi, Sakyoku, Kyoto, 606-8501, Japan
- Center for Integrative Medicine and Physics (CiMPhy), Institute for Advanced Study, Kyoto University, Yoshida-Honmachi, Sakyoku, Kyoto, 606-8501, Japan
- Physical Chemistry of Biosystems, Institute of Physical Chemistry, Heidelberg University, 69120, Heidelberg, Germany
| | - Jun Suzuki
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Yoshida-Honmachi, Sakyoku, Kyoto, 606-8501, Japan.
- Graduate School of Biostudies, Kyoto University, Konoe-cho, Yoshida, Sakyoku, Kyoto, 606-8501, Japan.
- Center for Integrated Biosystems, Institute for Biomedical Sciences, Academia Sinica, Taipei, Taiwan.
- CREST, Japan Science and Technology Agency, Kawaguchi, Saitama, 332-0012, Japan.
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7
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Bali A, Schaefer SP, Trier I, Zhang AL, Kabeche L, Paulsen CE. Molecular mechanism of hyperactivation conferred by a truncation of TRPA1. Nat Commun 2023; 14:2867. [PMID: 37208332 PMCID: PMC10199097 DOI: 10.1038/s41467-023-38542-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Accepted: 05/08/2023] [Indexed: 05/21/2023] Open
Abstract
A drastic TRPA1 mutant (R919*) identified in CRAMPT syndrome patients has not been mechanistically characterized. Here, we show that the R919* mutant confers hyperactivity when co-expressed with wild type (WT) TRPA1. Using functional and biochemical assays, we reveal that the R919* mutant co-assembles with WT TRPA1 subunits into heteromeric channels in heterologous cells that are functional at the plasma membrane. The R919* mutant hyperactivates channels by enhancing agonist sensitivity and calcium permeability, which could account for the observed neuronal hypersensitivity-hyperexcitability symptoms. We postulate that R919* TRPA1 subunits contribute to heteromeric channel sensitization by altering pore architecture and lowering energetic barriers to channel activation contributed by the missing regions. Our results expand the physiological impact of nonsense mutations, reveal a genetically tractable mechanism for selective channel sensitization, uncover insights into the process of TRPA1 gating, and provide an impetus for genetic analysis of patients with CRAMPT or other stochastic pain syndromes.
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Affiliation(s)
- Avnika Bali
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Samantha P Schaefer
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Isabelle Trier
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
- Cancer Biology Institute, Yale University, West Haven, CT, USA
| | - Alice L Zhang
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Lilian Kabeche
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
- Cancer Biology Institute, Yale University, West Haven, CT, USA
| | - Candice E Paulsen
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA.
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8
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Patel DC, Swift N, Tewari BP, Browning JL, Prim C, Chaunsali L, Kimbrough I, Olsen ML, Sontheimer H. Infection-induced epilepsy is caused by increased expression of chondroitin sulfate proteoglycans in hippocampus and amygdala. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.16.541066. [PMID: 37292901 PMCID: PMC10245664 DOI: 10.1101/2023.05.16.541066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Alterations in the extracellular matrix (ECM) are common in epilepsy, yet whether they are cause or consequence of disease is unknow. Using Theiler's virus infection model of acquired epilepsy we find de novo expression of chondroitin sulfate proteoglycans (CSPGs), a major ECM component, in dentate gyrus (DG) and amygdala exclusively in mice with seizures. Preventing synthesis of CSPGs specifically in DG and amygdala by deletion of major CSPG aggrecan reduced seizure burden. Patch-clamp recordings from dentate granule cells (DGCs) revealed enhanced intrinsic and synaptic excitability in seizing mice that was normalized by aggrecan deletion. In situ experiments suggest that DGCs hyperexcitability results from negatively charged CSPGs increasing stationary cations (K+, Ca2+) on the membrane thereby depolarizing neurons, increasing their intrinsic and synaptic excitability. We show similar changes in CSPGs in pilocarpine-induced epilepsy suggesting enhanced CSPGs in the DG and amygdala may be a common ictogenic factor and novel therapeutic potential.
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Affiliation(s)
- Dipan C Patel
- Department of Neuroscience, School of Medicine, University of Virginia, Charlottesville, VA 22903, USA
| | - Nathaniel Swift
- Department of Internal Medicine, Gerontology and Geriatric Medicine, School of Medicine, Wake Forest University, Winston-Salem, NC 27157, USA
| | - Bhanu P Tewari
- Department of Neuroscience, School of Medicine, University of Virginia, Charlottesville, VA 22903, USA
| | - Jack L Browning
- School of Neuroscience, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
| | - Courtney Prim
- Department of Neuroscience, School of Medicine, University of Virginia, Charlottesville, VA 22903, USA
| | - Lata Chaunsali
- Department of Neuroscience, School of Medicine, University of Virginia, Charlottesville, VA 22903, USA
| | - Ian Kimbrough
- Department of Neuroscience, School of Medicine, University of Virginia, Charlottesville, VA 22903, USA
| | - Michelle L Olsen
- School of Neuroscience, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
| | - Harald Sontheimer
- Department of Neuroscience, School of Medicine, University of Virginia, Charlottesville, VA 22903, USA
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9
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Cook DC, Ryan TA. GABA BR silencing of nerve terminals. eLife 2023; 12:e83530. [PMID: 37014052 PMCID: PMC10115440 DOI: 10.7554/elife.83530] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2022] [Accepted: 04/03/2023] [Indexed: 04/05/2023] Open
Abstract
Control of neurotransmission efficacy is central to theories of how the brain computes and stores information. Presynaptic G-protein coupled receptors (GPCRs) are critical in this problem as they locally influence synaptic strength and can operate on a wide range of time scales. Among the mechanisms by which GPCRs impact neurotransmission is by inhibiting voltage-gated calcium (Ca2+) influx in the active zone. Here, using quantitative analysis of both single bouton Ca2+ influx and exocytosis, we uncovered an unexpected non-linear relationship between the magnitude of action potential driven Ca2+ influx and the concentration of external Ca2+ ([Ca2+]e). We find that this unexpected relationship is leveraged by GPCR signaling when operating at the nominal physiological set point for [Ca2+]e, 1.2 mM, to achieve complete silencing of nerve terminals. These data imply that the information throughput in neural circuits can be readily modulated in an all-or-none fashion at the single synapse level when operating at the physiological set point.
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Affiliation(s)
- Daniel C Cook
- Department of Anesthesiology, Weill Cornell Medical CollegeNew YorkUnited States
| | - Timothy A Ryan
- Department of Anesthesiology, Weill Cornell Medical CollegeNew YorkUnited States
- Department of Biochemistry, Weill Cornell Medical CollegeNew YorkUnited States
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10
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Pawar A, Pardasani KR. Effect of disturbances in neuronal calcium and IP3 dynamics on β-amyloid production and degradation. Cogn Neurodyn 2023; 17:239-256. [PMID: 36704637 PMCID: PMC9871154 DOI: 10.1007/s11571-022-09815-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Revised: 04/12/2022] [Accepted: 04/21/2022] [Indexed: 01/29/2023] Open
Abstract
Overproduction and accumulation of β-amyloid and its improper clearance can cause neurotoxicity leading to Alzheimer's disease. The production and degradation of β-amyloid depend on the calcium ([Ca2+]) and IP3 dynamics in the nerve cells. Thus, there is a need to understand the impacts of disturbances in the processes of [Ca2+] and IP3 dynamics on β-amyloid production and its degradation. Here, a model is proposed to investigate the role of [Ca2+] and IP3 dynamics on β-amyloid production and degradation. The problem is formulated in terms of the initial boundary value problem involving the system of two reaction-diffusion equations respectively for [Ca2+] and IP3 in the nerve cell. The solution is obtained by employing the Finite element approach. The numerical results are used to analyze the impact of various mechanisms of calcium and IP3 dynamics on β-amyloid production and degradation in a neuron cell. The results indicate that disturbances in any of the constitutive processes of interdependent calcium and IP3 dynamics like source influx, buffering, serca pump, and IP3 dynamics, etc. can cause dynamic changes in β-amyloid production and degradation, which in turn can be the cause of neurotoxicity and neuronal disorders like Alzheimer's disease. Thus, the relationships obtained by the proposed model among various mechanisms can be useful in addressing the challenges of identifying specific constitutive processes causing neuronal disorders like Alzheimer's disease, etc., and developing the framework for their diagnosis and treatment.
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Affiliation(s)
- Anand Pawar
- Department of Mathematics, Bioinformatics, and Computer Applications, MANIT, Bhopal, Madhya Pradesh 462003 India
| | - Kamal Raj Pardasani
- Department of Mathematics, Bioinformatics, and Computer Applications, MANIT, Bhopal, Madhya Pradesh 462003 India
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11
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Knodel MM, Dutta Roy R, Wittum G. Influence of T-Bar on Calcium Concentration Impacting Release Probability. Front Comput Neurosci 2022; 16:855746. [PMID: 35586479 PMCID: PMC9108211 DOI: 10.3389/fncom.2022.855746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2022] [Accepted: 03/09/2022] [Indexed: 11/25/2022] Open
Abstract
The relation of form and function, namely the impact of the synaptic anatomy on calcium dynamics in the presynaptic bouton, is a major challenge of present (computational) neuroscience at a cellular level. The Drosophila larval neuromuscular junction (NMJ) is a simple model system, which allows studying basic effects in a rather simple way. This synapse harbors several special structures. In particular, in opposite to standard vertebrate synapses, the presynaptic boutons are rather large, and they have several presynaptic zones. In these zones, different types of anatomical structures are present. Some of the zones bear a so-called T-bar, a particular anatomical structure. The geometric form of the T-bar resembles the shape of the letter “T” or a table with one leg. When an action potential arises, calcium influx is triggered. The probability of vesicle docking and neurotransmitter release is superlinearly proportional to the concentration of calcium close to the vesicular release site. It is tempting to assume that the T-bar causes some sort of calcium accumulation and hence triggers a higher release probability and thus enhances neurotransmitter exocytosis. In order to study this influence in a quantitative manner, we constructed a typical T-bar geometry and compared the calcium concentration close to the active zones (AZs). We compared the case of synapses with and without T-bars. Indeed, we found a substantial influence of the T-bar structure on the presynaptic calcium concentrations close to the AZs, indicating that this anatomical structure increases vesicle release probability. Therefore, our study reveals how the T-bar zone implies a strong relation between form and function. Our study answers the question of experimental studies (namely “Wichmann and Sigrist, Journal of neurogenetics 2010”) concerning the sense of the anatomical structure of the T-bar.
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Affiliation(s)
- Markus M. Knodel
- Goethe Center for Scientific Computing (GCSC), Goethe Universität Frankfurt, Frankfurt, Germany
- *Correspondence: Markus M. Knodel ; orcid.org/0000-0001-8739-0803
| | | | - Gabriel Wittum
- Goethe Center for Scientific Computing (GCSC), Goethe Universität Frankfurt, Frankfurt, Germany
- Applied Mathematics and Computational Science, Computer, Electrical and Mathematical Science and Engineering Division, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
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12
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Mazzaferro S, Strikwerda JR, Sine SM. Stoichiometry-selective modulation of α4β2 nicotinic ACh receptors by divalent cations. Br J Pharmacol 2022; 179:1353-1370. [PMID: 34768309 DOI: 10.1111/bph.15723] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 10/11/2021] [Accepted: 10/18/2021] [Indexed: 02/03/2023] Open
Abstract
BACKGROUND AND PURPOSE α4β2 nicotinic ACh receptors (nAChRs) comprise the most abundant class of nAChRs in the nervous system. They assemble in two stoichiometric forms, each exhibiting distinct functional and pharmacological signatures. However, whether one or both forms are modulated by calcium or magnesium has not been established. EXPERIMENTAL APPROACH To assess the functional consequences of calcium and magnesium, each stoichiometric form was expressed in clonal mammalian fibroblasts and single-channel currents were recorded in the presence of a range of ACh concentrations. KEY RESULTS In the absence of divalent cations, each stoichiometric form exhibits high unitary conductance and simple gating kinetics composed of solitary channel openings or short bursts of openings. However, in the presence of calcium and magnesium, the conductance and gating kinetics change in a stoichiometry-dependent manner. Calcium and magnesium reduce the conductance of both stoichiometric forms, with each cation producing an equivalent reduction, but the reduction is greater for the (α4)2 (β2)3 form. Moreover, divalent cations promote efficient channel opening of the (α4)3 (β2)2 stoichiometry, while minimally affecting the (α4)2 (β2)3 stoichiometry. For the (α4)3 (β2)2 stoichiometry, at high but not low ACh concentrations, calcium in synergy with magnesium promote clustering of channel openings into episodes of many openings in quick succession. CONCLUSION AND IMPLICATIONS Modulation of the α4β2 nAChR by divalent cations depends on the ACh concentration, the type of cation and the subunit stoichiometry. The functional consequences of modulation are expected to depend on the regional distributions of the stoichiometric forms and synaptic versus extrasynaptic locations of the receptors.
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Affiliation(s)
- Simone Mazzaferro
- Receptor Biology Laboratory, Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota, USA
| | - John R Strikwerda
- Receptor Biology Laboratory, Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota, USA
| | - Steven M Sine
- Receptor Biology Laboratory, Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota, USA.,Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic College of Medicine, Rochester, Minnesota, USA.,Department of Neurology, Mayo Clinic College of Medicine, Rochester, Minnesota, USA
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13
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Mechanism of Zn 2+ and Ca 2+ Binding to Human S100A1. Biomolecules 2021; 11:biom11121823. [PMID: 34944467 PMCID: PMC8699212 DOI: 10.3390/biom11121823] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Revised: 11/26/2021] [Accepted: 11/30/2021] [Indexed: 12/18/2022] Open
Abstract
S100A1 is a member of the S100 family of small ubiquitous Ca2+-binding proteins, which participates in the regulation of cell differentiation, motility, and survival. It exists as homo- or heterodimers. S100A1 has also been shown to bind Zn2+, but the molecular mechanisms of this binding are not yet known. In this work, using ESI-MS and ITC, we demonstrate that S100A1 can coordinate 4 zinc ions per monomer, with two high affinity (KD~4 and 770 nm) and two low affinity sites. Using competitive binding experiments between Ca2+ and Zn2+ and QM/MM molecular modeling we conclude that Zn2+ high affinity sites are located in the EF-hand motifs of S100A1. In addition, two lower affinity sites can bind Zn2+ even when the EF-hands are saturated by Ca2+, resulting in a 2Ca2+:S100A1:2Zn2+ conformer. Finally, we show that, in contrast to calcium, an excess of Zn2+ produces a destabilizing effect on S100A1 structure and leads to its aggregation. We also determined a higher affinity to Ca2+ (KD~0.16 and 24 μm) than was previously reported for S100A1, which would allow this protein to function as a Ca2+/Zn2+-sensor both inside and outside cells, participating in diverse signaling pathways under normal and pathological conditions.
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14
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Genetically encoded cell-death indicators (GEDI) to detect an early irreversible commitment to neurodegeneration. Nat Commun 2021; 12:5284. [PMID: 34489414 PMCID: PMC8421388 DOI: 10.1038/s41467-021-25549-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Accepted: 08/16/2021] [Indexed: 01/07/2023] Open
Abstract
Cell death is a critical process that occurs normally in health and disease. However, its study is limited due to available technologies that only detect very late stages in the process or specific death mechanisms. Here, we report the development of a family of fluorescent biosensors called genetically encoded death indicators (GEDIs). GEDIs specifically detect an intracellular Ca2+ level that cells achieve early in the cell death process and that marks a stage at which cells are irreversibly committed to die. The time-resolved nature of a GEDI delineates a binary demarcation of cell life and death in real time, reformulating the definition of cell death. We demonstrate that GEDIs acutely and accurately report death of rodent and human neurons in vitro, and show that GEDIs enable an automated imaging platform for single cell detection of neuronal death in vivo in zebrafish larvae. With a quantitative pseudo-ratiometric signal, GEDIs facilitate high-throughput analysis of cell death in time-lapse imaging analysis, providing the necessary resolution and scale to identify early factors leading to cell death in studies of neurodegeneration. Cell death is a critical process in health and disease, yet available markers record later stages of cell death once a cell has already begun to decompose. Here the authors show the use of a genetically encoded calcium indicator that demarcates an irreversible stage of cell death earlier than previously possible.
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15
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Natarajan K, Mukhtasimova N, Corradi J, Lasala M, Bouzat C, Sine SM. Mechanism of calcium potentiation of the α7 nicotinic acetylcholine receptor. J Gen Physiol 2021; 152:151971. [PMID: 32702089 PMCID: PMC7478872 DOI: 10.1085/jgp.202012606] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Revised: 05/19/2020] [Accepted: 06/22/2020] [Indexed: 12/14/2022] Open
Abstract
The α7 nicotinic acetylcholine receptor (nAChR) is among the most abundant types of nAChR in the brain, yet the ability of nerve-released ACh to activate α7 remains enigmatic. In particular, a major population of α7 resides in extra-synaptic regions where the ACh concentration is reduced, owing to dilution and enzymatic hydrolysis, yet ACh shows low potency in activating α7. Using high-resolution single-channel recording techniques, we show that extracellular calcium is a powerful potentiator of α7 activated by low concentrations of ACh. Potentiation manifests as robust increases in the frequency of channel opening and the average duration of the openings. Molecular dynamics simulations reveal that calcium binds to the periphery of the five ligand binding sites and is framed by a pair of anionic residues from the principal and complementary faces of each site. Mutation of residues identified by simulation prevents calcium from potentiating ACh-elicited channel opening. An anionic residue is conserved at each of the identified positions in all vertebrate species of α7. Thus, calcium associates with a novel structural motif on α7 and is an obligate cofactor in regions of limited ACh concentration.
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Affiliation(s)
- Kathiresan Natarajan
- Receptor Biology Laboratory, Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN
| | - Nuriya Mukhtasimova
- Receptor Biology Laboratory, Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN
| | - Jeremías Corradi
- Instituto de Investigaciones Bioquímicas, Departamento de Biologia, Bioquimica y Farmacia, Universidad Nacional del Sur-Consejo Nacional de Investigaciones Científicas y Técnicas, Bahía Blanca, Argentina
| | - Matías Lasala
- Instituto de Investigaciones Bioquímicas, Departamento de Biologia, Bioquimica y Farmacia, Universidad Nacional del Sur-Consejo Nacional de Investigaciones Científicas y Técnicas, Bahía Blanca, Argentina
| | - Cecilia Bouzat
- Instituto de Investigaciones Bioquímicas, Departamento de Biologia, Bioquimica y Farmacia, Universidad Nacional del Sur-Consejo Nacional de Investigaciones Científicas y Técnicas, Bahía Blanca, Argentina
| | - Steven M Sine
- Receptor Biology Laboratory, Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN.,Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic College of Medicine, Rochester, MN.,Department of Neurology, Mayo Clinic College of Medicine, Rochester, MN
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16
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Ashby JW, Mack JJ. Endothelial Control of Cerebral Blood Flow. THE AMERICAN JOURNAL OF PATHOLOGY 2021; 191:1906-1916. [PMID: 33713686 DOI: 10.1016/j.ajpath.2021.02.023] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Revised: 02/09/2021] [Accepted: 02/24/2021] [Indexed: 12/19/2022]
Abstract
Since constant perfusion of blood throughout the brain is critical for neuronal health, the regulation of cerebral blood flow is complex and highly controlled. This regulation is controlled, in part, by the cerebral endothelium. In this review, multiple modes of endothelium-derived blood flow regulation is discussed, including chemical control of vascular tone, heterotypic and homotypic cell-cell interactions, second messenger signaling, and cellular response to physical forces and inflammatory mediators. Because cerebral small vessel disease is often associated with endothelial dysfunction and a compromised blood-brain barrier, understanding the endothelial factors that regulate vessel function to maintain cerebral blood flow and prevent vascular permeability may provide insights into disease prevention and treatment.
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Affiliation(s)
- Julianne W Ashby
- Division of Cardiology, Department of Medicine, University of California, Los Angeles, California
| | - Julia J Mack
- Division of Cardiology, Department of Medicine, University of California, Los Angeles, California.
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17
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Wei M, Lin P, Chen Y, Lee JY, Zhang L, Li F, Ling D. Applications of ion level nanosensors for neuroscience research. Nanomedicine (Lond) 2020; 15:2871-2881. [PMID: 33252311 DOI: 10.2217/nnm-2020-0320] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Ion activities are tightly associated with brain physiology, such as intracranial cell membrane potential, neural activity and neuropathology. Thus, monitoring the ion levels in the brain is of great significance in neuroscience research. Recently, nanosensors have emerged as powerful tools for monitoring brain ion levels and dynamics. With controllable structures and functions, nanosensors have been intensively used for monitoring neural activity and cell function and can be used in disease diagnosis. Here, we summarize the recent advances in the design and application of ion level nanosensors at different physiological levels, aiming to draw a connection of the interrelated intracranial ion activities. Furthermore, perspectives on the rationally designed ion level nanosensors in understanding the brain functions are highlighted.
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Affiliation(s)
- Min Wei
- Institute of Pharmaceutics, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
| | - Peihua Lin
- Institute of Pharmaceutics, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
| | - Ying Chen
- Institute of Pharmaceutics, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
| | - Ji Young Lee
- Institute of Pharmaceutics, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
| | - Lingxiao Zhang
- Institute of Pharmaceutics, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
| | - Fangyuan Li
- Institute of Pharmaceutics, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China.,Hangzhou Institute of Innovative Medicine, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China.,Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
| | - Daishun Ling
- Institute of Pharmaceutics, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China.,Hangzhou Institute of Innovative Medicine, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China.,Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China.,Key Laboratory of Biomedical Engineering of the Ministry of Education, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou 310058, China
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18
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McCrorie P, Mistry J, Taresco V, Lovato T, Fay M, Ward I, Ritchie AA, Clarke PA, Smith SJ, Marlow M, Rahman R. Etoposide and olaparib polymer-coated nanoparticles within a bioadhesive sprayable hydrogel for post-surgical localised delivery to brain tumours. Eur J Pharm Biopharm 2020; 157:108-120. [PMID: 33068736 DOI: 10.1016/j.ejpb.2020.10.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Revised: 10/07/2020] [Accepted: 10/11/2020] [Indexed: 02/09/2023]
Abstract
Glioblastoma is a malignant brain tumour with a median survival of 14.6 months from diagnosis. Despite maximal surgical resection and concurrent chemoradiotherapy, reoccurrence is inevitable. To try combating the disease at a stage of low residual tumour burden immediately post-surgery, we propose a localised drug delivery system comprising of a spray device, bioadhesive hydrogel (pectin) and drug nanocrystals coated with polylactic acid-polyethylene glycol (NCPPs), to be administered directly into brain parenchyma adjacent to the surgical cavity. We have repurposed pectin for use within the brain, showing in vitro and in vivo biocompatibility, bio-adhesion to mammalian brain and gelling at physiological brain calcium concentrations. Etoposide and olaparib NCPPs with high drug loading have shown in vitro stability and drug release over 120 h. Pluronic F127 stabilised NCPPs to ensure successful spraying, as determined by dynamic light scattering and transmission electron microscopy. Successful delivery of Cy5-labelled NCPPs was demonstrated in a large ex vivo mammalian brain, with NCPP present in the tissue surrounding the resection cavity. Our data collectively demonstrates the pre-clinical development of a novel localised delivery device based on a sprayable hydrogel containing therapeutic NCPPs, amenable for translation to intracranial surgical resection models for the treatment of malignant brain tumours.
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Affiliation(s)
- Phoebe McCrorie
- Children's Brain Tumour Research Centre, Biodiscovery Institute, School of Medicine, University of Nottingham, NG7 2RD, UK
| | - Jatin Mistry
- Division of Advanced Materials and Healthcare Technologies, School of Pharmacy, University of Nottingham, NG7 2RD, UK
| | - Vincenzo Taresco
- Division of Advanced Materials and Healthcare Technologies, School of Pharmacy, University of Nottingham, NG7 2RD, UK
| | - Tatiana Lovato
- Division of Advanced Materials and Healthcare Technologies, School of Pharmacy, University of Nottingham, NG7 2RD, UK
| | - Michael Fay
- Division of Advanced Materials and Healthcare Technologies, School of Pharmacy, University of Nottingham, NG7 2RD, UK
| | - Ian Ward
- School of Life Sciences Imaging, School of Life Sciences, University of Nottingham, NG7 2RD, UK
| | - Alison A Ritchie
- Division of Cancer and Stem Cells, Faculty of Medicine and Health Sciences, University of Nottingham, NG7 2RD, UK
| | - Philip A Clarke
- Division of Cancer and Stem Cells, Faculty of Medicine and Health Sciences, University of Nottingham, NG7 2RD, UK
| | - Stuart J Smith
- Children's Brain Tumour Research Centre, Biodiscovery Institute, School of Medicine, University of Nottingham, NG7 2RD, UK
| | - Maria Marlow
- Division of Advanced Materials and Healthcare Technologies, School of Pharmacy, University of Nottingham, NG7 2RD, UK.
| | - Ruman Rahman
- Children's Brain Tumour Research Centre, Biodiscovery Institute, School of Medicine, University of Nottingham, NG7 2RD, UK.
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19
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Rasmussen R, O'Donnell J, Ding F, Nedergaard M. Interstitial ions: A key regulator of state-dependent neural activity? Prog Neurobiol 2020; 193:101802. [PMID: 32413398 PMCID: PMC7331944 DOI: 10.1016/j.pneurobio.2020.101802] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 03/24/2020] [Accepted: 03/26/2020] [Indexed: 02/08/2023]
Abstract
Throughout the nervous system, ion gradients drive fundamental processes. Yet, the roles of interstitial ions in brain functioning is largely forgotten. Emerging literature is now revitalizing this area of neuroscience by showing that interstitial cations (K+, Ca2+ and Mg2+) are not static quantities but change dynamically across states such as sleep and locomotion. In turn, these state-dependent changes are capable of sculpting neuronal activity; for example, changing the local interstitial ion composition in the cortex is sufficient for modulating the prevalence of slow-frequency neuronal oscillations, or potentiating the gain of visually evoked responses. Disturbances in interstitial ionic homeostasis may also play a central role in the pathogenesis of central nervous system diseases. For example, impairments in K+ buffering occur in a number of neurodegenerative diseases, and abnormalities in neuronal activity in disease models disappear when interstitial K+ is normalized. Here we provide an overview of the roles of interstitial ions in physiology and pathology. We propose the brain uses interstitial ion signaling as a global mechanism to coordinate its complex activity patterns, and ion homeostasis failure contributes to central nervous system diseases affecting cognitive functions and behavior.
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Affiliation(s)
- Rune Rasmussen
- Center for Translational Neuromedicine, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark.
| | - John O'Donnell
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY, 14642, United States
| | - Fengfei Ding
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY, 14642, United States
| | - Maiken Nedergaard
- Center for Translational Neuromedicine, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark; Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY, 14642, United States.
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20
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Guagliardo NA, Klein PM, Gancayco CA, Lu A, Leng S, Makarem RR, Cho C, Rusin CG, Breault DT, Barrett PQ, Beenhakker MP. Angiotensin II induces coordinated calcium bursts in aldosterone-producing adrenal rosettes. Nat Commun 2020; 11:1679. [PMID: 32245948 PMCID: PMC7125102 DOI: 10.1038/s41467-020-15408-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Accepted: 02/28/2020] [Indexed: 12/15/2022] Open
Abstract
Aldosterone-producing zona glomerulosa (zG) cells of the adrenal gland arrange in distinct multi-cellular rosettes that provide a structural framework for adrenal cortex morphogenesis and plasticity. Whether this cyto-architecture also plays functional roles in signaling remains unexplored. To determine if structure informs function, we generated mice with zG-specific expression of GCaMP3 and imaged zG cells within their native rosette structure. Here we demonstrate that within the rosette, angiotensin II evokes periodic Cav3-dependent calcium events that form bursts that are stereotypic in form. Our data reveal a critical role for angiotensin II in regulating burst occurrence, and a multifunctional role for the rosette structure in activity-prolongation and coordination. Combined our data define the calcium burst as the fundamental unit of zG layer activity evoked by angiotensin II and highlight a novel role for the rosette as a facilitator of cell communication.
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Affiliation(s)
| | - Peter M Klein
- Departments of Pharmacology, Charlottesville, VA, USA
- Neuroscience Graduate Program, University of Virginia, Charlottesville, VA, USA
| | | | - Adam Lu
- Departments of Pharmacology, Charlottesville, VA, USA
- Neuroscience Graduate Program, University of Virginia, Charlottesville, VA, USA
| | - Sining Leng
- Division of Endocrinology, Boston Children's Hospital, Boston, MA, USA
| | | | - Chelsea Cho
- Departments of Pharmacology, Charlottesville, VA, USA
| | - Craig G Rusin
- Department of Pediatrics-Cardiology, Baylor College of Medicine, and Harvard Stem Cell Institute, Cambridge, MA, USA
| | - David T Breault
- Division of Endocrinology, Boston Children's Hospital, Boston, MA, USA
| | | | - Mark P Beenhakker
- Departments of Pharmacology, Charlottesville, VA, USA.
- Neuroscience Graduate Program, University of Virginia, Charlottesville, VA, USA.
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21
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Synaptic Plasticity Shapes Brain Connectivity: Implications for Network Topology. Int J Mol Sci 2019; 20:ijms20246193. [PMID: 31817968 PMCID: PMC6940892 DOI: 10.3390/ijms20246193] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 12/02/2019] [Accepted: 12/06/2019] [Indexed: 12/13/2022] Open
Abstract
Studies of brain network connectivity improved understanding on brain changes and adaptation in response to different pathologies. Synaptic plasticity, the ability of neurons to modify their connections, is involved in brain network remodeling following different types of brain damage (e.g., vascular, neurodegenerative, inflammatory). Although synaptic plasticity mechanisms have been extensively elucidated, how neural plasticity can shape network organization is far from being completely understood. Similarities existing between synaptic plasticity and principles governing brain network organization could be helpful to define brain network properties and reorganization profiles after damage. In this review, we discuss how different forms of synaptic plasticity, including homeostatic and anti-homeostatic mechanisms, could be directly involved in generating specific brain network characteristics. We propose that long-term potentiation could represent the neurophysiological basis for the formation of highly connected nodes (hubs). Conversely, homeostatic plasticity may contribute to stabilize network activity preventing poor and excessive connectivity in the peripheral nodes. In addition, synaptic plasticity dysfunction may drive brain network disruption in neuropsychiatric conditions such as Alzheimer's disease and schizophrenia. Optimal network architecture, characterized by efficient information processing and resilience, and reorganization after damage strictly depend on the balance between these forms of plasticity.
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22
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Suresh A, Hung A. Structural effects of divalent calcium cations on the α7 nicotinic acetylcholine receptor: A molecular dynamics simulation study. Proteins 2019; 87:992-1005. [PMID: 31228282 DOI: 10.1002/prot.25761] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 05/27/2019] [Accepted: 06/15/2019] [Indexed: 12/11/2022]
Abstract
The α7 subtype of neuronal nicotinic acetylcholine receptor (nAChR) is a ligand-gated ion channel protein that is vital to various neurological functions, including modulation of neurotransmitter release. A relatively high concentration of extracellular Ca2+ in the neuronal environment is likely to exert substantial structural and functional influence on nAChRs, which may affect their interactions with agonists and antagonists. In this work, we employed atomistic molecular dynamics (MD) simulations to examine the effects of elevated Ca2+ on the structure and dynamics of α7 nAChR embedded in a model phospholipid bilayer. Our results suggest that the presence of Ca2+ in the α7 nAChR environment results in closure of loop C-in the extracellular ligand-binding domain, a motion normally associated with agonist binding and receptor activation. Elevated Ca2+ also alters the conformation of key regions of the receptor, including the inter-helical loops, pore-lining helices and the "gate" residues, and causes partial channel opening in the absence of an agonist, leading to an attendant reduction in the free energy of Ca2+ permeation through the pore as elucidated by umbrella sampling simulations. Overall, the structural and permeability changes in α7 nAChR suggest that elevated Ca2+ induces a partially activated receptor state that is distinct from both the resting and the agonist-activated states. These results are consistent with the notion that divalent ions can serve as a potentiator of nAChRs, resulting in a higher rate of receptor activation (and subsequent desensitization) in the presence of agonists, with possible implications for diseases involving calcium dysregulation.
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Affiliation(s)
- Abishek Suresh
- School of Science, RMIT University, Melbourne, Victoria, Australia
| | - Andrew Hung
- School of Science, RMIT University, Melbourne, Victoria, Australia
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23
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Kim J, Leahy W, Shlizerman E. Neural Interactome: Interactive Simulation of a Neuronal System. Front Comput Neurosci 2019; 13:8. [PMID: 30930759 PMCID: PMC6425397 DOI: 10.3389/fncom.2019.00008] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Accepted: 01/30/2019] [Indexed: 01/14/2023] Open
Abstract
Connectivity and biophysical processes determine the functionality of neuronal networks. We, therefore, developed a real-time framework, called Neural Interactome,, to simultaneously visualize and interact with the structure and dynamics of such networks. Neural Interactome is a cross-platform framework, which combines graph visualization with the simulation of neural dynamics, or experimentally recorded multi neural time series, to allow application of stimuli to neurons to examine network responses. In addition, Neural Interactome supports structural changes, such as disconnection of neurons from the network (ablation feature). Neural dynamics can be explored on a single neuron level (using a zoom feature), back in time (using a review feature), and recorded (using presets feature). The development of the Neural Interactome was guided by generic concepts to be applicable to neuronal networks with different neural connectivity and dynamics. We implement the framework using a model of the nervous system of Caenorhabditis elegans (C. elegans) nematode, a model organism with resolved connectome and neural dynamics. We show that Neural Interactome assists in studying neural response patterns associated with locomotion and other stimuli. In particular, we demonstrate how stimulation and ablation help in identifying neurons that shape particular dynamics. We examine scenarios that were experimentally studied, such as touch response circuit, and explore new scenarios that did not undergo elaborate experimental studies.
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Affiliation(s)
- Jimin Kim
- Department of Electrical and Computer Engineering, University of Washington, Seattle, WA, United States
| | - William Leahy
- Department of Applied Mathematics, University of Washington, Seattle, WA, United States
| | - Eli Shlizerman
- Department of Electrical and Computer Engineering, University of Washington, Seattle, WA, United States.,Department of Applied Mathematics, University of Washington, Seattle, WA, United States
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24
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Mirzakhalili E, Epureanu BI, Gourgou E. A mathematical and computational model of the calcium dynamics in Caenorhabditis elegans ASH sensory neuron. PLoS One 2018; 13:e0201302. [PMID: 30048509 PMCID: PMC6062085 DOI: 10.1371/journal.pone.0201302] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Accepted: 05/28/2018] [Indexed: 12/31/2022] Open
Abstract
We propose a mathematical and computational model that captures the stimulus-generated Ca2+ transients in the C. elegans ASH sensory neuron. The rationale is to develop a tool that will enable a cross-talk between modeling and experiments, using modeling results to guide targeted experimental efforts. The model is built based on biophysical events and molecular cascades known to unfold as part of neurons' Ca2+ homeostasis mechanism, as well as on Ca2+ signaling events. The state of ion channels is described by their probability of being activated or inactivated, and the remaining molecular states are based on biochemically defined kinetic equations or known biochemical motifs. We estimate the parameters of the model using experimental data of hyperosmotic stimulus-evoked Ca2+ transients detected with a FRET sensor in young and aged worms, unstressed and exposed to oxidative stress. We use a hybrid optimization method composed of a multi-objective genetic algorithm and nonlinear least-squares to estimate the model parameters. We first obtain the model parameters for young unstressed worms. Next, we use these values of the parameters as a starting point to identify the model parameters for stressed and aged worms. We show that the model, in combination with experimental data, corroborates literature results. In addition, we demonstrate that our model can be used to predict ASH response to complex combinations of stimulation pulses. The proposed model includes for the first time the ASH Ca2+ dynamics observed during both "on" and "off" responses. This mathematical and computational effort is the first to propose a dynamic model of the Ca2+ transients' mechanism in C. elegans neurons, based on biochemical pathways of the cell's Ca2+ homeostasis machinery. We believe that the proposed model can be used to further elucidate the Ca2+ dynamics of a key C. elegans neuron, to guide future experiments on C. elegans neurobiology, and to pave the way for the development of more mathematical models for neuronal Ca2+ dynamics.
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Affiliation(s)
- Ehsan Mirzakhalili
- Mechanical Engineering Department, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Bogdan I. Epureanu
- Mechanical Engineering Department, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Eleni Gourgou
- Mechanical Engineering Department, University of Michigan, Ann Arbor, Michigan, United States of America
- Department of Internal Medicine, Division of Geriatrics, Medical School, University of Michigan, Ann Arbor, Michigan, United States of America
- * E-mail:
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Okada S, Bartelle BB, Li N, Breton-Provencher V, Lee JJ, Rodriguez E, Melican J, Sur M, Jasanoff A. Calcium-dependent molecular fMRI using a magnetic nanosensor. NATURE NANOTECHNOLOGY 2018; 13:473-477. [PMID: 29713073 PMCID: PMC6086382 DOI: 10.1038/s41565-018-0092-4] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Accepted: 02/13/2018] [Indexed: 05/22/2023]
Abstract
Calcium ions are ubiquitous signalling molecules in all multicellular organisms, where they mediate diverse aspects of intracellular and extracellular communication over widely varying temporal and spatial scales 1 . Though techniques to map calcium-related activity at a high resolution by optical means are well established, there is currently no reliable method to measure calcium dynamics over large volumes in intact tissue 2 . Here, we address this need by introducing a family of magnetic calcium-responsive nanoparticles (MaCaReNas) that can be detected by magnetic resonance imaging (MRI). MaCaReNas respond within seconds to [Ca2+] changes in the 0.1-1.0 mM range, suitable for monitoring extracellular calcium signalling processes in the brain. We show that the probes permit the repeated detection of brain activation in response to diverse stimuli in vivo. MaCaReNas thus provide a tool for calcium-activity mapping in deep tissue and offer a precedent for the development of further nanoparticle-based sensors for dynamic molecular imaging with MRI.
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Affiliation(s)
- Satoshi Okada
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Benjamin B Bartelle
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Nan Li
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Vincent Breton-Provencher
- Department of Brain & Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
- Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Jiyoung J Lee
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Elisenda Rodriguez
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - James Melican
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Mriganka Sur
- Department of Brain & Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
- Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Alan Jasanoff
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA.
- Department of Brain & Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA.
- Department of Nuclear Science & Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA.
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Kurowski P, Grzelka K, Szulczyk P. Ionic Mechanism Underlying Rebound Depolarization in Medial Prefrontal Cortex Pyramidal Neurons. Front Cell Neurosci 2018; 12:93. [PMID: 29740284 PMCID: PMC5924806 DOI: 10.3389/fncel.2018.00093] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Accepted: 03/21/2018] [Indexed: 12/19/2022] Open
Abstract
Rebound depolarization (RD) occurs after membrane hyperpolarization and converts an arriving inhibitory signal into cell excitation. The purpose of our study was to clarify the ionic mechanism of RD in synaptically isolated layer V medial prefrontal cortex (mPFC) pyramidal neurons in slices obtained from 58- to 62-day-old male rats. The RD was evoked after a step hyperpolarization below -80 mV, longer than 150 ms in 192 of 211 (91%) tested neurons. The amplitude of RD was 30.6 ± 1.2 mV above the resting membrane potential (-67.9 ± 0.95 mV), and it lasted a few 100 ms (n = 192). RD could be observed only after preventing BK channel activation, which was attained either by using paxilline, by removal of Ca++ from the extra- or intracellular solution, by blockade of Ca++ channels or during protein kinase C (PKC) activation. RD was resistant to tetrodotoxin (TTX) and was abolished after the removal of Na+ from the extracellular solution or application of an anti-Nav1.9 antibody to the cell interior. We conclude that two membrane currents are concomitantly activated after the step hyperpolarization in the tested neurons: a. a low-threshold, TTX-resistant, Na+ current that evokes RD; and b. an outward K+ current through BK channels that opposes Na+-dependent depolarization. The obtained results also suggest that a. low-level Ca++ in the external medium attained upon intense neuronal activity may facilitate the formation of RD and seizures; and b. RD can be evoked during the activation of PKC, which is an effector of a number of transduction pathways.
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Affiliation(s)
- Przemysław Kurowski
- Laboratory of Physiology and Pathophysiology, Center for Preclinical Research and Technology, The Medical University of Warsaw, Warsaw, Poland
| | - Katarzyna Grzelka
- Laboratory of Physiology and Pathophysiology, Center for Preclinical Research and Technology, The Medical University of Warsaw, Warsaw, Poland
| | - Paweł Szulczyk
- Laboratory of Physiology and Pathophysiology, Center for Preclinical Research and Technology, The Medical University of Warsaw, Warsaw, Poland
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Gerbino A, Colella M. The Different Facets of Extracellular Calcium Sensors: Old and New Concepts in Calcium-Sensing Receptor Signalling and Pharmacology. Int J Mol Sci 2018; 19:E999. [PMID: 29584660 PMCID: PMC5979557 DOI: 10.3390/ijms19040999] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Revised: 03/23/2018] [Accepted: 03/25/2018] [Indexed: 12/14/2022] Open
Abstract
The current interest of the scientific community for research in the field of calcium sensing in general and on the calcium-sensing Receptor (CaR) in particular is demonstrated by the still increasing number of papers published on this topic. The extracellular calcium-sensing receptor is the best-known G-protein-coupled receptor (GPCR) able to sense external Ca2+ changes. Widely recognized as a fundamental player in systemic Ca2+ homeostasis, the CaR is ubiquitously expressed in the human body where it activates multiple signalling pathways. In this review, old and new notions regarding the mechanisms by which extracellular Ca2+ microdomains are created and the tools available to measure them are analyzed. After a survey of the main signalling pathways triggered by the CaR, a special attention is reserved for the emerging concepts regarding CaR function in the heart, CaR trafficking and pharmacology. Finally, an overview on other Ca2+ sensors is provided.
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Affiliation(s)
- Andrea Gerbino
- Department of Biosciences, Biotechnology and Biopharmaceutics, University of Bari, 70121 Bari, Italy.
| | - Matilde Colella
- Department of Biosciences, Biotechnology and Biopharmaceutics, University of Bari, 70121 Bari, Italy.
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Hu HJ, Song M. Disrupted Ionic Homeostasis in Ischemic Stroke and New Therapeutic Targets. J Stroke Cerebrovasc Dis 2017; 26:2706-2719. [PMID: 29054733 DOI: 10.1016/j.jstrokecerebrovasdis.2017.09.011] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Revised: 08/30/2017] [Accepted: 09/06/2017] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Stroke is a leading cause of long-term disability. All neuroprotectants targeting excitotoxicity have failed to become stroke medications. In order to explore and identify new therapeutic targets for stroke, we here reviewed present studies of ionic transporters and channels that are involved in ischemic brain damage. METHOD We surveyed recent literature from animal experiments and clinical reports in the databases of PubMed and Elsevier ScienceDirect to analyze ionic mechanisms underlying ischemic cell damage and suggest promising ideas for stroke therapy. RESULTS Dysfunction of ionic transporters and disrupted ionic homeostasis are most early changes that underlie ischemic brain injury, thus receiving sustained attention in translational stroke research. The Na+/K+-ATPase, Na+/Ca2+ Exchanger, ionotropic glutamate receptor, acid-sensing ion channels (ASICs), sulfonylurea receptor isoform 1 (SUR1)-regulated NCCa-ATP channels, and transient receptor potential (TRP) channels are critically involved in ischemia-induced cellular degenerating processes such as cytotoxic edema, excitotoxicity, necrosis, apoptosis, and autophagic cell death. Some ionic transporters/channels also act as signalosomes to regulate cell death signaling. For acute stroke treatment, glutamate-mediated excitotoxicity must be interfered within 2 hours after stroke. The SUR1-regulated NCCa-ATP channels, Na+/K+-ATPase, ASICs, and TRP channels have a much longer therapeutic window, providing new therapeutic targets for developing feasible pharmacological treatments toward acute ischemic stroke. CONCLUSION The next generation of stroke therapy can apply a polypharmacology strategy for which drugs are designed to target multiple ion transporters/channels or their interaction with neurotoxic signaling pathways. But a successful translation of neuroprotectants relies on in-depth analyses of cell death mechanisms and suitable animal models resembling human stroke.
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Affiliation(s)
- Hui-Jie Hu
- Department of Pharmacology, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Mingke Song
- Department of Pharmacology, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
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Nicholson C, Hrabětová S. Brain Extracellular Space: The Final Frontier of Neuroscience. Biophys J 2017; 113:2133-2142. [PMID: 28755756 DOI: 10.1016/j.bpj.2017.06.052] [Citation(s) in RCA: 178] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Revised: 05/31/2017] [Accepted: 06/07/2017] [Indexed: 01/15/2023] Open
Abstract
Brain extracellular space is the narrow microenvironment that surrounds every cell of the central nervous system. It contains a solution that closely resembles cerebrospinal fluid with the addition of extracellular matrix molecules. The space provides a reservoir for ions essential to the electrical activity of neurons and forms an intercellular chemical communication channel. Attempts to reveal the size and structure of the extracellular space using electron microscopy have had limited success; however, a biophysical approach based on diffusion of selected probe molecules has proved useful. A point-source paradigm, realized in the real-time iontophoresis method using tetramethylammonium, as well as earlier radiotracer methods, have shown that the extracellular space occupies ∼20% of brain tissue and small molecules have an effective diffusion coefficient that is two-fifths that in a free solution. Monte Carlo modeling indicates that geometrical constraints, including dead-space microdomains, contribute to the hindrance to diffusion. Imaging the spread of macromolecules shows them increasingly hindered as a function of size and suggests that the gaps between cells are predominantly ∼40 nm with wider local expansions that may represent dead-spaces. Diffusion measurements also characterize interactions of ions and proteins with the chondroitin and heparan sulfate components of the extracellular matrix; however, the many roles of the matrix are only starting to become apparent. The existence and magnitude of bulk flow and the so-called glymphatic system are topics of current interest and controversy. The extracellular space is an exciting area for research that will be propelled by emerging technologies.
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Affiliation(s)
- Charles Nicholson
- Department of Neuroscience and Physiology, New York University School of Medicine, New York, New York; Department of Cell Biology, State University of New York Downstate Medical Center, Brooklyn, New York.
| | - Sabina Hrabětová
- Department of Cell Biology, State University of New York Downstate Medical Center, Brooklyn, New York; The Robert Furchgott Center for Neural and Behavioral Science, State University of New York Downstate Medical Center, Brooklyn, New York
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30
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Colella M, Gerbino A, Hofer AM, Curci S. Recent advances in understanding the extracellular calcium-sensing receptor. F1000Res 2016; 5. [PMID: 27803801 PMCID: PMC5074356 DOI: 10.12688/f1000research.8963.1] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 10/13/2016] [Indexed: 12/11/2022] Open
Abstract
The extracellular calcium-sensing receptor (CaR), a ubiquitous class C G-protein-coupled receptor (GPCR), is responsible for the control of calcium homeostasis in body fluids. It integrates information about external Ca
2+ and a surfeit of other endogenous ligands into multiple intracellular signals, but how is this achieved? This review will focus on some of the exciting concepts in CaR signaling and pharmacology that have emerged in the last few years.
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Affiliation(s)
- Matilde Colella
- Department of Biosciences, Biotechnology and Biopharmaceutics, University of Bari , Bari, Italy
| | - Andrea Gerbino
- Department of Biosciences, Biotechnology and Biopharmaceutics, University of Bari , Bari, Italy
| | - Aldebaran M Hofer
- Department of Surgery, Brigham & Women's Hospital, Harvard Medical School and VA Boston Healthcare System, West Roxbury, MA, USA
| | - Silvana Curci
- Department of Surgery, Brigham & Women's Hospital, Harvard Medical School and VA Boston Healthcare System, West Roxbury, MA, USA
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31
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Jones BL, Smith SM. Calcium-Sensing Receptor: A Key Target for Extracellular Calcium Signaling in Neurons. Front Physiol 2016; 7:116. [PMID: 27065884 PMCID: PMC4811949 DOI: 10.3389/fphys.2016.00116] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Accepted: 03/14/2016] [Indexed: 12/14/2022] Open
Abstract
Though both clinicians and scientists have long recognized the influence of extracellular calcium on the function of muscle and nervous tissue, recent insights reveal that the mechanisms allowing changes in extracellular calcium to alter cellular excitability have been incompletely understood. For many years the effects of calcium on neuronal signaling were explained only in terms of calcium entry through voltage-gated calcium channels and biophysical charge screening. More recently however, it has been recognized that the calcium-sensing receptor is prevalent in the nervous system and regulates synaptic transmission and neuronal activity via multiple signaling pathways. Here we review the multiplicity of mechanisms by which changes in extracellular calcium alter neuronal signaling and propose that multiple mechanisms are required to describe the full range of experimental observations.
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Affiliation(s)
- Brian L. Jones
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Oregon Health & Science UniversityPortland, OR, USA
| | - Stephen M. Smith
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Oregon Health & Science UniversityPortland, OR, USA
- Section of Pulmonary and Critical Care Medicine, VA Portland Health Care SystemPortland, OR, USA
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32
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Nanoparticle delivery and particle diffusion in confined and complex environments. J Drug Deliv Sci Technol 2015. [DOI: 10.1016/j.jddst.2015.06.017] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Law R, Levin M. Bioelectric memory: modeling resting potential bistability in amphibian embryos and mammalian cells. Theor Biol Med Model 2015; 12:22. [PMID: 26472354 PMCID: PMC4608135 DOI: 10.1186/s12976-015-0019-9] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Accepted: 09/27/2015] [Indexed: 12/20/2022] Open
Abstract
Background Bioelectric gradients among all cells, not just within excitable nerve and muscle, play instructive roles in developmental and regenerative pattern formation. Plasma membrane resting potential gradients regulate cell behaviors by regulating downstream transcriptional and epigenetic events. Unlike neurons, which fire rapidly and typically return to the same polarized state, developmental bioelectric signaling involves many cell types stably maintaining various levels of resting potential during morphogenetic events. It is important to begin to quantitatively model the stability of bioelectric states in cells, to understand computation and pattern maintenance during regeneration and remodeling. Method To facilitate the analysis of endogenous bioelectric signaling and the exploitation of voltage-based cellular controls in synthetic bioengineering applications, we sought to understand the conditions under which somatic cells can stably maintain distinct resting potential values (a type of state memory). Using the Channelpedia ion channel database, we generated an array of amphibian oocyte and mammalian membrane models for voltage evolution. These models were analyzed and searched, by simulation, for a simple dynamical property, multistability, which forms a type of voltage memory. Results We find that typical mammalian models and amphibian oocyte models exhibit bistability when expressing different ion channel subsets, with either persistent sodium or inward-rectifying potassium, respectively, playing a facilitative role in bistable memory formation. We illustrate this difference using fast sodium channel dynamics for which a comprehensive theory exists, where the same model exhibits bistability under mammalian conditions but not amphibian conditions. In amphibians, potassium channels from the Kv1.x and Kv2.x families tend to disrupt this bistable memory formation. We also identify some common principles under which physiological memory emerges, which suggest specific strategies for implementing memories in bioengineering contexts. Conclusion Our results reveal conditions under which cells can stably maintain one of several resting voltage potential values. These models suggest testable predictions for experiments in developmental bioelectricity, and illustrate how cells can be used as versatile physiological memory elements in synthetic biology, and unconventional computation contexts. Electronic supplementary material The online version of this article (doi:10.1186/s12976-015-0019-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Robert Law
- Department of Neuroscience, Brown University, Box G, Providence, RI, 02912, USA.
| | - Michael Levin
- Department of Biology and Tufts Center for Regenerative and Developmental Biology, Tufts University, 200 Boston Avenue, Medford, MA, 02155, USA.
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Tora AS, Rovira X, Dione I, Bertrand H, Brabet I, De Koninck Y, Doyon N, Pin J, Acher F, Goudet C. Allosteric modulation of metabotropic glutamate receptors by chloride ions. FASEB J 2015; 29:4174-88. [DOI: 10.1096/fj.14-269746] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 06/15/2015] [Indexed: 11/11/2022]
Affiliation(s)
- Amélie S. Tora
- Institut de Génomique Fonctionnelle, CNRS, UMR 5203, Université de MontpellierMontpellierFrance
- INSERM U1191MontpellierFrance
| | - Xavier Rovira
- Institut de Génomique Fonctionnelle, CNRS, UMR 5203, Université de MontpellierMontpellierFrance
- INSERM U1191MontpellierFrance
| | - Ibrahima Dione
- Centre de Recherche de l'Institut Universitaire en Santé Mentale du Québec and Université LavalQuébecCanada
| | | | - Isabelle Brabet
- Institut de Génomique Fonctionnelle, CNRS, UMR 5203, Université de MontpellierMontpellierFrance
- INSERM U1191MontpellierFrance
| | - Yves De Koninck
- Centre de Recherche de l'Institut Universitaire en Santé Mentale du Québec and Université LavalQuébecCanada
| | - Nicolas Doyon
- Centre de Recherche de l'Institut Universitaire en Santé Mentale du Québec and Université LavalQuébecCanada
| | - Jean‐Philippe Pin
- Institut de Génomique Fonctionnelle, CNRS, UMR 5203, Université de MontpellierMontpellierFrance
- INSERM U1191MontpellierFrance
| | - Francine Acher
- Laboratoire de Chimie et Biochimie Pharmacologiques et ToxicologiquesCNRS, UMR 8601, Université Paris Descartes, Sorbonne Paris CitéParisFrance
| | - Cyril Goudet
- Institut de Génomique Fonctionnelle, CNRS, UMR 5203, Université de MontpellierMontpellierFrance
- INSERM U1191MontpellierFrance
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Delattre V, Keller D, Perich M, Markram H, Muller EB. Network-timing-dependent plasticity. Front Cell Neurosci 2015; 9:220. [PMID: 26106298 PMCID: PMC4460533 DOI: 10.3389/fncel.2015.00220] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Accepted: 05/22/2015] [Indexed: 11/13/2022] Open
Abstract
Bursts of activity in networks of neurons are thought to convey salient information and drive synaptic plasticity. Here we report that network bursts also exert a profound effect on Spike-Timing-Dependent Plasticity (STDP). In acute slices of juvenile rat somatosensory cortex we paired a network burst, which alone induced long-term depression (LTD), with STDP-induced long-term potentiation (LTP) and LTD. We observed that STDP-induced LTP was either unaffected, blocked or flipped into LTD by the network burst, and that STDP-induced LTD was either saturated or flipped into LTP, depending on the relative timing of the network burst with respect to spike coincidences of the STDP event. We hypothesized that network bursts flip STDP-induced LTP to LTD by depleting resources needed for LTP and therefore developed a resource-dependent STDP learning rule. In a model neural network under the influence of the proposed resource-dependent STDP rule, we found that excitatory synaptic coupling was homeostatically regulated to produce power law distributed burst amplitudes reflecting self-organized criticality, a state that ensures optimal information coding.
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Affiliation(s)
- Vincent Delattre
- Laboratory of Neural Microcircuitry, Brain and Mind Institute, École Polytechnique Fédérale de Lausanne Lausanne, Switzerland
| | - Daniel Keller
- Center for Brain Simulation, École Polytechnique Fédérale de Lausanne Geneva, Switzerland
| | - Matthew Perich
- Center for Brain Simulation, École Polytechnique Fédérale de Lausanne Geneva, Switzerland ; Department of Biomedical Engineering, Northwestern University, Evanston IL, USA
| | - Henry Markram
- Laboratory of Neural Microcircuitry, Brain and Mind Institute, École Polytechnique Fédérale de Lausanne Lausanne, Switzerland ; Center for Brain Simulation, École Polytechnique Fédérale de Lausanne Geneva, Switzerland
| | - Eilif B Muller
- Center for Brain Simulation, École Polytechnique Fédérale de Lausanne Geneva, Switzerland
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36
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Morquette P, Verdier D, Kadala A, Féthière J, Philippe AG, Robitaille R, Kolta A. An astrocyte-dependent mechanism for neuronal rhythmogenesis. Nat Neurosci 2015; 18:844-54. [PMID: 25938883 DOI: 10.1038/nn.4013] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Accepted: 04/02/2015] [Indexed: 12/22/2022]
Abstract
Communication between neurons rests on their capacity to change their firing pattern to encode different messages. For several vital functions, such as respiration and mastication, neurons need to generate a rhythmic firing pattern. Here we show in the rat trigeminal sensori-motor circuit for mastication that this ability depends on regulation of the extracellular Ca(2+) concentration ([Ca(2+)]e) by astrocytes. In this circuit, astrocytes respond to sensory stimuli that induce neuronal rhythmic activity, and their blockade with a Ca(2+) chelator prevents neurons from generating a rhythmic bursting pattern. This ability is restored by adding S100β, an astrocytic Ca(2+)-binding protein, to the extracellular space, while application of an anti-S100β antibody prevents generation of rhythmic activity. These results indicate that astrocytes regulate a fundamental neuronal property: the capacity to change firing pattern. These findings may have broad implications for many other neural networks whose functions depend on the generation of rhythmic activity.
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Affiliation(s)
- Philippe Morquette
- Département de Neurosciences and Groupe de Recherche sur le Système Nerveux Central, Université de Montréal, Montréal, Québec, Canada
| | - Dorly Verdier
- Département de Neurosciences and Groupe de Recherche sur le Système Nerveux Central, Université de Montréal, Montréal, Québec, Canada
| | - Aklesso Kadala
- Département de Neurosciences and Groupe de Recherche sur le Système Nerveux Central, Université de Montréal, Montréal, Québec, Canada
| | - James Féthière
- Faculté de Pharmacie, Université de Montréal, Montréal, Québec, Canada
| | - Antony G Philippe
- 1] Faculté des Sciences du Sport, Université Montpellier 1, Montpellier, France. [2] Institut National de la Recherche Agronomique, UMR866 Dynamique Musculaire Et Métabolisme, Montpellier, France
| | - Richard Robitaille
- Département de Neurosciences and Groupe de Recherche sur le Système Nerveux Central, Université de Montréal, Montréal, Québec, Canada
| | - Arlette Kolta
- 1] Département de Neurosciences and Groupe de Recherche sur le Système Nerveux Central, Université de Montréal, Montréal, Québec, Canada. [2] Faculté de Médecine Dentaire and Réseau de Recherche en Santé Bucco-dentaire et Osseuse du Fonds de Recherche Québec-Santé, Université de Montréal, Montréal, Québec, Canada
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Wong CO, Chen K, Lin YQ, Chao Y, Duraine L, Lu Z, Yoon WH, Sullivan JM, Broadhead GT, Sumner CJ, Lloyd TE, Macleod GT, Bellen HJ, Venkatachalam K. A TRPV channel in Drosophila motor neurons regulates presynaptic resting Ca2+ levels, synapse growth, and synaptic transmission. Neuron 2014; 84:764-77. [PMID: 25451193 DOI: 10.1016/j.neuron.2014.09.030] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/10/2014] [Indexed: 12/30/2022]
Abstract
Presynaptic resting Ca(2+) influences synaptic vesicle (SV) release probability. Here, we report that a TRPV channel, Inactive (Iav), maintains presynaptic resting [Ca(2+)] by promoting Ca(2+) release from the endoplasmic reticulum in Drosophila motor neurons, and is required for both synapse development and neurotransmission. We find that Iav activates the Ca(2+)/calmodulin-dependent protein phosphatase calcineurin, which is essential for presynaptic microtubule stabilization at the neuromuscular junction. Thus, loss of Iav induces destabilization of presynaptic microtubules, resulting in diminished synaptic growth. Interestingly, expression of human TRPV1 in Iav-deficient motor neurons rescues these defects. We also show that the absence of Iav causes lower SV release probability and diminished synaptic transmission, whereas Iav overexpression elevates these synaptic parameters. Together, our findings indicate that Iav acts as a key regulator of synaptic development and function by influencing presynaptic resting [Ca(2+)].
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Affiliation(s)
- Ching-On Wong
- Department of Integrative Biology and Pharmacology, University of Texas School of Medicine, 6431 Fannin Street, Houston, TX 77030, USA
| | - Kuchuan Chen
- Graduate Program in Developmental Biology, Baylor College of Medicine, 1250 Moursund Street, Suite N1125.14, Mailstop NR-1125, Houston, TX 77030, USA
| | - Yong Qi Lin
- Howard Hughes Medical Institute; Departments of Molecular and Human Genetics and Neuroscience, Baylor College of Medicine, 1250 Moursund Street, Suite N1125.14, Mailstop NR-1125, Houston, TX 77030, USA
| | - Yufang Chao
- Department of Integrative Biology and Pharmacology, University of Texas School of Medicine, 6431 Fannin Street, Houston, TX 77030, USA
| | - Lita Duraine
- Howard Hughes Medical Institute; Departments of Molecular and Human Genetics and Neuroscience, Baylor College of Medicine, 1250 Moursund Street, Suite N1125.14, Mailstop NR-1125, Houston, TX 77030, USA
| | - Zhongmin Lu
- Integrative Biology and Neuroscience program, Florida Atlantic University and Max Planck Florida Institute, 5353 Parkside Drive, Jupiter, FL 33458, USA
| | - Wan Hee Yoon
- Howard Hughes Medical Institute; Departments of Molecular and Human Genetics and Neuroscience, Baylor College of Medicine, 1250 Moursund Street, Suite N1125.14, Mailstop NR-1125, Houston, TX 77030, USA
| | - Jeremy M Sullivan
- Department of Neurology, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Baltimore, MD 21231, USA
| | - Geoffrey T Broadhead
- Department of Integrative Biology and Pharmacology, University of Texas School of Medicine, 6431 Fannin Street, Houston, TX 77030, USA
| | - Charlotte J Sumner
- Department of Neurology, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Baltimore, MD 21231, USA; Department of Neuroscience, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Baltimore, MD 21231, USA
| | - Thomas E Lloyd
- Department of Neurology, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Baltimore, MD 21231, USA; Department of Neuroscience, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Baltimore, MD 21231, USA
| | - Gregory T Macleod
- Department of Physiology, University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, TX 78229, USA
| | - Hugo J Bellen
- Graduate Program in Developmental Biology, Baylor College of Medicine, 1250 Moursund Street, Suite N1125.14, Mailstop NR-1125, Houston, TX 77030, USA; Howard Hughes Medical Institute; Departments of Molecular and Human Genetics and Neuroscience, Baylor College of Medicine, 1250 Moursund Street, Suite N1125.14, Mailstop NR-1125, Houston, TX 77030, USA
| | - Kartik Venkatachalam
- Department of Integrative Biology and Pharmacology, University of Texas School of Medicine, 6431 Fannin Street, Houston, TX 77030, USA; Graduate Program in Developmental Biology, Baylor College of Medicine, 1250 Moursund Street, Suite N1125.14, Mailstop NR-1125, Houston, TX 77030, USA; Graduate Programs in Cell and Regulatory Biology (CRB) and Neuroscience, Graduate School of Biomedical Sciences, University of Texas School of Medicine, Houston, TX 77030.
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Grein S, Stepniewski M, Reiter S, Knodel MM, Queisser G. 1D-3D hybrid modeling-from multi-compartment models to full resolution models in space and time. Front Neuroinform 2014; 8:68. [PMID: 25120463 PMCID: PMC4114301 DOI: 10.3389/fninf.2014.00068] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Accepted: 06/28/2014] [Indexed: 12/03/2022] Open
Abstract
Investigation of cellular and network dynamics in the brain by means of modeling and simulation has evolved into a highly interdisciplinary field, that uses sophisticated modeling and simulation approaches to understand distinct areas of brain function. Depending on the underlying complexity, these models vary in their level of detail, in order to cope with the attached computational cost. Hence for large network simulations, single neurons are typically reduced to time-dependent signal processors, dismissing the spatial aspect of each cell. For single cell or networks with relatively small numbers of neurons, general purpose simulators allow for space and time-dependent simulations of electrical signal processing, based on the cable equation theory. An emerging field in Computational Neuroscience encompasses a new level of detail by incorporating the full three-dimensional morphology of cells and organelles into three-dimensional, space and time-dependent, simulations. While every approach has its advantages and limitations, such as computational cost, integrated and methods-spanning simulation approaches, depending on the network size could establish new ways to investigate the brain. In this paper we present a hybrid simulation approach, that makes use of reduced 1D-models using e.g., the NEURON simulator—which couples to fully resolved models for simulating cellular and sub-cellular dynamics, including the detailed three-dimensional morphology of neurons and organelles. In order to couple 1D- and 3D-simulations, we present a geometry-, membrane potential- and intracellular concentration mapping framework, with which graph- based morphologies, e.g., in the swc- or hoc-format, are mapped to full surface and volume representations of the neuron and computational data from 1D-simulations can be used as boundary conditions for full 3D simulations and vice versa. Thus, established models and data, based on general purpose 1D-simulators, can be directly coupled to the emerging field of fully resolved, highly detailed 3D-modeling approaches. We present the developed general framework for 1D/3D hybrid modeling and apply it to investigate electrically active neurons and their intracellular spatio-temporal calcium dynamics.
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Affiliation(s)
- Stephan Grein
- Computational Neuroscience, Goethe Center for Scientific Computing, Computer Science and Mathematics, Goethe University Frankfurt am Main, Germany
| | - Martin Stepniewski
- Computational Neuroscience, Goethe Center for Scientific Computing, Computer Science and Mathematics, Goethe University Frankfurt am Main, Germany
| | - Sebastian Reiter
- Simulation and Modelling, Goethe Center for Scientific Computing, Computer Science and Mathematics, Goethe University Frankfurt am Main, Germany
| | - Markus M Knodel
- Simulation and Modelling, Goethe Center for Scientific Computing, Computer Science and Mathematics, Goethe University Frankfurt am Main, Germany
| | - Gillian Queisser
- Computational Neuroscience, Goethe Center for Scientific Computing, Computer Science and Mathematics, Goethe University Frankfurt am Main, Germany
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Tanwar J, Datta A, Chauhan K, Kumaran SS, Tiwari AK, Kadiyala KG, Pal S, Thirumal M, Mishra AK. Design and synthesis of calcium responsive magnetic resonance imaging agent: Its relaxation and luminescence studies. Eur J Med Chem 2014; 82:225-32. [PMID: 24904969 DOI: 10.1016/j.ejmech.2014.05.046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2013] [Revised: 05/15/2014] [Accepted: 05/20/2014] [Indexed: 10/25/2022]
Abstract
Calcium concentration modulation both inside and outside cell is of considerable interest for nervous system function in normal and pathological conditions. MRI has potential for very high spatial resolution at molecular/cellular level. Design, synthesis and evaluation of Gd-DO3A-AME-NPHE, a calcium responsive MRI contrast agent is presented. The probe is comprised of a Gd(3+)-DO3A core coupled to iminoacetate coordinating groups for calcium induced relaxivity switching. In the absence of Ca(2+) ions, inner sphere water binding to the Gd-DO3A-AME-NPHE is restricted with longitudinal relaxivity, r1 = 4.37 mM(-1) s(-1) at 4.7 T. However, addition of Ca(2+) triggers a marked enhancement in r1 = 6.99 mM(-1) s(-1) at 4.7 T (60% increase). The construct is highly selective for Ca(2+) over competitive metal ions at extracellular concentration. The r1 is modulated by changes in the hydration number (0.2 to 1.05), which was confirmed by luminescence emission lifetimes of the analogous Eu(3+) complex. T1 phantom images establish the capability of complex of visualizing changes in [Ca(2+)] by MRI.
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Affiliation(s)
- Jyoti Tanwar
- Institute of Nuclear Medicine and Allied Sciences, Brig S. K. Mazumdar Road, Delhi 110054, India; Department of Chemistry, University of Delhi, Delhi 110054, India
| | - Anupama Datta
- Institute of Nuclear Medicine and Allied Sciences, Brig S. K. Mazumdar Road, Delhi 110054, India.
| | - Kanchan Chauhan
- Institute of Nuclear Medicine and Allied Sciences, Brig S. K. Mazumdar Road, Delhi 110054, India
| | - S Senthil Kumaran
- Department of N.M.R. and MRI, All India Institute of Medical Sciences, New Delhi, India
| | - Anjani K Tiwari
- Institute of Nuclear Medicine and Allied Sciences, Brig S. K. Mazumdar Road, Delhi 110054, India
| | - K Ganesh Kadiyala
- Institute of Nuclear Medicine and Allied Sciences, Brig S. K. Mazumdar Road, Delhi 110054, India; Department of Chemistry, University of Delhi, Delhi 110054, India
| | - Sunil Pal
- Institute of Nuclear Medicine and Allied Sciences, Brig S. K. Mazumdar Road, Delhi 110054, India
| | - M Thirumal
- Department of Chemistry, University of Delhi, Delhi 110054, India
| | - Anil K Mishra
- Institute of Nuclear Medicine and Allied Sciences, Brig S. K. Mazumdar Road, Delhi 110054, India.
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40
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Rebollido-Rios R, Bandari S, Wilms C, Jakuschev S, Vortkamp A, Grobe K, Hoffmann D. Signaling domain of Sonic Hedgehog as cannibalistic calcium-regulated zinc-peptidase. PLoS Comput Biol 2014; 10:e1003707. [PMID: 25033298 PMCID: PMC4102407 DOI: 10.1371/journal.pcbi.1003707] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2013] [Accepted: 05/22/2014] [Indexed: 12/30/2022] Open
Abstract
Sonic Hedgehog (Shh) is a representative of the evolutionary closely related class of Hedgehog proteins that have essential signaling functions in animal development. The N-terminal domain (ShhN) is also assigned to the group of LAS proteins (LAS = Lysostaphin type enzymes, D-Ala-D-Ala metalloproteases, Sonic Hedgehog), of which all members harbor a structurally well-defined Zn2+ center; however, it is remarkable that ShhN so far is the only LAS member without proven peptidase activity. Another unique feature of ShhN in the LAS group is a double-Ca2+ center close to the zinc. We have studied the effect of these calcium ions on ShhN structure, dynamics, and interactions. We find that the presence of calcium has a marked impact on ShhN properties, with the two calcium ions having different effects. The more strongly bound calcium ion significantly stabilizes the overall structure. Surprisingly, the binding of the second calcium ion switches the putative catalytic center from a state similar to LAS enzymes to a state that probably is catalytically inactive. We describe in detail the mechanics of the switch, including the effect on substrate co-ordinating residues and on the putative catalytic water molecule. The properties of the putative substrate binding site suggest that ShhN could degrade other ShhN molecules, e.g. by cleavage at highly conserved glycines in ShhN. To test experimentally the stability of ShhN against autodegradation, we compare two ShhN mutants in vitro: (1) a ShhN mutant unable to bind calcium but with putative catalytic center intact, and thus, according to our hypothesis, a constitutively active peptidase, and (2) a mutant carrying additionally mutation E177A, i.e., with the putative catalytically active residue knocked out. The in vitro results are consistent with ShhN being a cannibalistic zinc-peptidase. These experiments also reveal that the peptidase activity depends on pH.
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Affiliation(s)
- Rocio Rebollido-Rios
- Research Group Bioinformatics, Faculty of Biology, Center of Medical Biotechnology, University of Duisburg-Essen, Essen, Germany
| | - Shyam Bandari
- Institute of Physiological Chemistry and Pathobiochemistry, Faculty of Medicine, University of Münster, Münster, Germany
| | - Christoph Wilms
- Research Group Bioinformatics, Faculty of Biology, Center of Medical Biotechnology, University of Duisburg-Essen, Essen, Germany
| | - Stanislav Jakuschev
- Research Group Bioinformatics, Faculty of Biology, Center of Medical Biotechnology, University of Duisburg-Essen, Essen, Germany
| | - Andrea Vortkamp
- Department of Developmental Biology, Faculty of Biology, Center of Medical Biotechnology, University of Duisburg-Essen, Essen, Germany
| | - Kay Grobe
- Institute of Physiological Chemistry and Pathobiochemistry, Faculty of Medicine, University of Münster, Münster, Germany
| | - Daniel Hoffmann
- Research Group Bioinformatics, Faculty of Biology, Center of Medical Biotechnology, University of Duisburg-Essen, Essen, Germany
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41
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Smith MD, Cruz L. Changes to the Structure and Dynamics in Mutations of Aβ21–30 Caused by Ions in Solution. J Phys Chem B 2013; 117:14907-15. [DOI: 10.1021/jp408579v] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Micholas Dean Smith
- Department
of Physics, Drexel University, 3141 Chestnut Street, Philadelphia 19104, Pennsylvania, United States
| | - Luis Cruz
- Department
of Physics, Drexel University, 3141 Chestnut Street, Philadelphia 19104, Pennsylvania, United States
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42
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The Cav3-Kv4 complex acts as a calcium sensor to maintain inhibitory charge transfer during extracellular calcium fluctuations. J Neurosci 2013; 33:7811-24. [PMID: 23637173 DOI: 10.1523/jneurosci.5384-12.2013] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Synaptic transmission and neuronal excitability depend on the concentration of extracellular calcium ([Ca](o)), yet repetitive synaptic input is known to decrease [Ca](o) in numerous brain regions. In the cerebellar molecular layer, synaptic input reduces [Ca](o) by up to 0.4 mm in the vicinity of stellate cell interneurons and Purkinje cell dendrites. The mechanisms used to maintain network excitability and Purkinje cell output in the face of this rapid change in calcium gradient have remained an enigma. Here we use single and dual patch recordings in an in vitro slice preparation of Sprague Dawley rats to investigate the effects of physiological decreases in [Ca](o) on the excitability of cerebellar stellate cells and their inhibitory regulation of Purkinje cells. We find that a Ca(v)3-K(v)4 ion channel complex expressed in stellate cells acts as a calcium sensor that responds to a decrease in [Ca]o by dynamically adjusting stellate cell output to maintain inhibitory charge transfer to Purkinje cells. The Ca(v)3-K(v)4 complex thus enables an adaptive regulation of inhibitory input to Purkinje cells during fluctuations in [Ca](o), providing a homeostatic control mechanism to regulate Purkinje cell excitability during repetitive afferent activity.
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Calcium homeostasis modulator 1 (CALHM1) is the pore-forming subunit of an ion channel that mediates extracellular Ca2+ regulation of neuronal excitability. Proc Natl Acad Sci U S A 2012; 109:E1963-71. [PMID: 22711817 DOI: 10.1073/pnas.1204023109] [Citation(s) in RCA: 111] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Extracellular Ca(2+) (Ca(2+)(o)) plays important roles in physiology. Changes of Ca(2+)(o) concentration ([Ca(2+)](o)) have been observed to modulate neuronal excitability in various physiological and pathophysiological settings, but the mechanisms by which neurons detect [Ca(2+)](o) are not fully understood. Calcium homeostasis modulator 1 (CALHM1) expression was shown to induce cation currents in cells and elevate cytoplasmic Ca(2+) concentration ([Ca(2+)](i)) in response to removal of Ca(2+)(o) and its subsequent addback. However, it is unknown whether CALHM1 is a pore-forming ion channel or modulates endogenous ion channels. Here we identify CALHM1 as the pore-forming subunit of a plasma membrane Ca(2+)-permeable ion channel with distinct ion permeability properties and unique coupled allosteric gating regulation by voltage and [Ca(2+)](o). Furthermore, we show that CALHM1 is expressed in mouse cortical neurons that respond to reducing [Ca(2+)](o) with enhanced conductance and action potential firing and strongly elevated [Ca(2+)](i) upon Ca(2+)(o) removal and its addback. In contrast, these responses are strongly muted in neurons from mice with CALHM1 genetically deleted. These results demonstrate that CALHM1 is an evolutionarily conserved ion channel family that detects membrane voltage and extracellular Ca(2+) levels and plays a role in cortical neuronal excitability and Ca(2+) homeostasis, particularly in response to lowering [Ca(2+)](o) and its restoration to normal levels.
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Abstract
Over the past decade, rapid signal exchange between astroglia and neurons across the interstitial space emerged as an essential element of synaptic circuit functioning in the brain. How and where exactly this exchange occurs in various physiological scenarios and the underlying cellular cascades remain a subject of intense study. The excitatory neurotransmitter glutamate and the inhibitory neurotransmitter γ-aminobutyric acid are thought to be the primary signal carriers that are regularly dispatched by active synapses to engage target receptors and transporters on the surface of astrocytes. New evidence identifies another ubiquitous messenger, extracellular calcium ions (Ca(2+)), which can report neural network activity to astroglia. Astrocytes in the hippocampus can respond to activity-induced partial Ca(2+) depletion in the extracellular space by generating prominent intracellular Ca(2+) waves. The underlying Ca(2+) sensing mechanism is proposed to involve the opening of the hemichannel connexin 43 in astrocytes, which in turn triggers the release of adenosine triphosphate to boost the activity of inhibitory interneurons, thus potentially providing negative feedback to tame excessive excitatory activity of neural circuits.
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Affiliation(s)
- Dmitri A Rusakov
- University College London Institute of Neurology, UCL, WC1N 3BG, London, UK.
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45
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Martin GV, Yun Y, Conforti L. Modulation of T cell activation by localized K⁺ accumulation at the immunological synapse--a mathematical model. J Theor Biol 2012; 300:173-82. [PMID: 22285786 DOI: 10.1016/j.jtbi.2012.01.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Revised: 12/21/2011] [Accepted: 01/11/2012] [Indexed: 01/06/2023]
Abstract
The response of T cells to antigens (T cell activation) is marked by an increase in intracellular Ca²⁺ levels. Voltage-gated and Ca²⁺-dependent K⁺ channels control the membrane potential of human T cells and regulate Ca²⁺ influx. This regulation is dependent on proper accumulation of K⁺ channels at the immunological synapse (IS) a signaling zone that forms between a T cell and antigen presenting cell. It is believed that the IS provides a site for regulation of the activation response and that K⁺ channel inhibition occurs at the IS, but the underlying mechanisms are unknown. A mathematical model was developed to test whether K⁺ efflux through K⁺ channels leads to an accumulation of K⁺ in the IS cleft, ultimately reducing K⁺ channel function and intracellular Ca²⁺ concentration ([Ca²⁺](i)). Simulations were conducted in models of resting and activated T cell subsets, which express different levels of K⁺ channels, by varying the K⁺ diffusion constant and the spatial localization of K⁺ channels at the IS. K⁺ accumulation in the IS cleft was calculated to increase K⁺ concentration ([K⁺]) from its normal value of 5.0 mM to 5.2-10.0 mM. Including K⁺ accumulation in the model of the IS reduced calculated K⁺ current by 1-12% and consequently, reduced calculated [Ca²⁺](i) by 1-28%. Significant reductions in K⁺ current and [Ca²⁺](i) only occurred in activated T cell simulations when most K⁺ channels were centrally clustered at the IS. The results presented show that the localization of K⁺ channels at the IS can produce a rise in [K⁺] in the IS cleft and lead to a substantial decrease in K⁺ currents and [Ca²⁺](i) in activated T cells thus providing a feedback inhibitory mechanism during T cell activation.
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Affiliation(s)
- Geoffrey V Martin
- Department of Internal Medicine, 231 A. Sabin Way, Division of Nephrology, University of Cincinnati, Cincinnati, OH 45267-0585, USA
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46
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Calcium-dependent dynamics of cadherin interactions at cell-cell junctions. Proc Natl Acad Sci U S A 2011; 108:9857-62. [PMID: 21613566 DOI: 10.1073/pnas.1019003108] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cadherins play a key role in the dynamics of cell-cell contact formation and remodeling of junctions and tissues. Cadherin-cadherin interactions are gated by extracellular Ca(2+), which serves to rigidify the cadherin extracellular domains and promote trans junctional interactions. Here we describe the direct visualization and quantification of spatiotemporal dynamics of N-cadherin interactions across intercellular junctions in living cells using a genetically encodable FRET reporter system. Direct measurements of transjunctional cadherin interactions revealed a sudden, but partial, loss of homophilic interactions (τ = 1.17 ± 0.06 s(-1)) upon chelation of extracellular Ca(2+). A cadherin mutant with reduced adhesive activity (W2A) exhibited a faster, more substantial loss of homophilic interactions (τ = 0.86 ± 0.02 s(-1)), suggesting two types of native cadherin interactions--one that is rapidly modulated by changes in extracellular Ca(2+) and another with relatively stable adhesive activity that is Ca(2+) independent. The Ca(2+)-sensitive dynamics of cadherin interactions were transmitted to the cell interior where β-catenin translocated to N-cadherin at the junction in both cells. These data indicate that cadherins can rapidly convey dynamic information about the extracellular environment to both cells that comprise a junction.
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47
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Chanda S, Oh S, Xu-Friedman MA. Calcium imaging of auditory nerve fiber terminals in the cochlear nucleus. J Neurosci Methods 2010; 195:24-9. [PMID: 21108967 DOI: 10.1016/j.jneumeth.2010.11.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2010] [Revised: 11/09/2010] [Accepted: 11/10/2010] [Indexed: 11/16/2022]
Abstract
One important model for understanding neuronal computation is how auditory information is transformed at the synapses made by auditory nerve (AN) fibers on the bushy cells (BCs) in the anteroventral cochlear nucleus (AVCN). This transformation is influenced by synaptic plasticity, the mechanisms of which have been studied primarily using postsynaptic electrophysiology. However, it is also important to make direct measurements of the presynaptic terminal to consider presynaptic mechanisms. Here we introduce a technique for doing that using calcium imaging of presynaptic AN terminals, by injecting dextran-conjugated fluorophores into the cochlea. To measure the calcium transients, we used calcium-sensitive fluorophores, and measured the changes in fluorescence upon stimulation. As an example of the application of this technique, we showed that activation of GABA(B) receptors reduces presynaptic calcium influx. This technique could be further extended to study the effects of activity- and other neuromodulator-dependent plasticities on AN terminals.
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Affiliation(s)
- Soham Chanda
- Department of Biological Sciences, University at Buffalo, State University of New York, Buffalo, NY 14260, USA
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48
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Liu H, Shim AHR, He X. Structural characterization of the ectodomain of a disintegrin and metalloproteinase-22 (ADAM22), a neural adhesion receptor instead of metalloproteinase: insights on ADAM function. J Biol Chem 2009; 284:29077-86. [PMID: 19692335 PMCID: PMC2781453 DOI: 10.1074/jbc.m109.014258] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2009] [Revised: 08/10/2009] [Indexed: 12/22/2022] Open
Abstract
ADAMs (a disintegrin and metalloproteinases) are a family of multidomain transmembrane glycoproteins with diverse roles in physiology and diseases, with several members being drug targets for cancer and inflammation therapies. The spatial organization of the ADAM extracellular segment and its influence on the function of ADAMs have been unclear. Although most members of the ADAM family are active zinc metalloproteinases, 8 of 21 ADAMs lack functional metalloproteinase domains and are implicated in protein-protein interactions instead of membrane protein ectodomain shedding. One of such non-proteinase ADAMs, ADAM22, acts as a receptor on the surface of the postsynaptic neuron to regulate synaptic signal transmission. The crystal structure of the full ectodomain of mature human ADAM22 shows that it is a compact four-leaf clover with the metalloproteinase-like domain held in the concave face of a rigid module formed by the disintegrin, cysteine-rich, and epidermal growth factor-like domains. The loss of metalloproteinase activity is ensured by the absence of critical catalytic residues, the filling of the substrate groove, and the steric hindrance by the cysteine-rich domain. The structure, combined with calorimetric experiments, suggests distinct roles of three putative calcium ions bound to ADAM22, with one in the metalloproteinase-like domain being regulatory and two in the disintegrin domain being structural. The metalloproteinase-like domain contacts the rest of ADAM22 with discontinuous, hydrophilic, and poorly complemented interactions, suggesting the possibility of modular movement of ADAM22 and other ADAMs. The ADAM22 structure provides a framework for understanding how different ADAMs exert their adhesive function and shedding activities.
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Affiliation(s)
- Heli Liu
- From the Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611
| | - Ann H. R. Shim
- From the Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611
| | - Xiaolin He
- From the Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611
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49
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Astrocytic dysfunction in epileptogenesis: consequence of altered potassium and glutamate homeostasis? J Neurosci 2009; 29:10588-99. [PMID: 19710312 DOI: 10.1523/jneurosci.2323-09.2009] [Citation(s) in RCA: 213] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Focal epilepsy often develops following traumatic, ischemic, or infectious brain injury. While the electrical activity of the epileptic brain is well characterized, the mechanisms underlying epileptogenesis are poorly understood. We have recently shown that in the rat neocortex, long-lasting breakdown of the blood-brain barrier (BBB) or direct exposure of the neocortex to serum-derived albumin leads to rapid upregulation of the astrocytic marker GFAP (glial fibrillary acidic protein), followed by delayed (within 4-7 d) development of an epileptic focus. We investigated the role of astrocytes in epileptogenesis in the BBB-breakdown and albumin models of epileptogenesis. We found similar, robust changes in astrocytic gene expression in the neocortex within hours following treatment with deoxycholic acid (BBB breakdown) or albumin. These changes predict reduced clearance capacity for both extracellular glutamate and potassium. Electrophysiological recordings in vitro confirmed the reduced clearance of activity-dependent accumulation of both potassium and glutamate 24 h following exposure to albumin. We used a NEURON model to simulate the consequences of reduced astrocytic uptake of potassium and glutamate on EPSPs. The model predicted that the accumulation of glutamate is associated with frequency-dependent (>100 Hz) decreased facilitation of EPSPs, while potassium accumulation leads to frequency-dependent (10-50 Hz) and NMDA-dependent synaptic facilitation. In vitro electrophysiological recordings during epileptogenesis confirmed frequency-dependent synaptic facilitation leading to seizure-like activity. Our data indicate a transcription-mediated astrocytic transformation early during epileptogenesis. We suggest that the resulting reduction in the clearance of extracellular potassium underlies frequency-dependent neuronal hyperexcitability and network synchronization.
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50
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Hrabetová S, Masri D, Tao L, Xiao F, Nicholson C. Calcium diffusion enhanced after cleavage of negatively charged components of brain extracellular matrix by chondroitinase ABC. J Physiol 2009; 587:4029-49. [PMID: 19546165 DOI: 10.1113/jphysiol.2009.170092] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The concentration of extracellular calcium plays a critical role in synaptic transmission and neuronal excitability as well as other physiological processes. The time course and extent of local fluctuations in the concentration of this ion largely depend on its effective diffusion coefficient (D*) and it has been speculated that fixed negative charges on chondroitin sulphate proteoglycans (CSPGs) and other components of the extracellular matrix may influence calcium diffusion because it is a divalent cation. In this study we used ion-selective microelectrodes combined with pressure ejection or iontophoresis of ions from a micropipette to quantify diffusion characteristics of neocortex and hippocampus in rat brain slices. We show that D* for calcium is less than the value predicted from the behaviour of the monovalent cation tetramethylammonium (TMA), a commonly used diffusion probe, but D* for calcium increases in both brain regions after the slices are treated with chondroitinase ABC, an enzyme that predominantly cleaves chondroitin sulphate glycans. These results suggest that CSPGs do play a role in determining the local diffusion properties of calcium in brain tissue, most likely through electrostatic interactions mediating rapid equilibrium binding. In contrast, chondroitinase ABC does not affect either the TMA diffusion or the extracellular volume fraction, indicating that the enzyme does not alter the structure of the extracellular space and that the diffusion of small monovalent cations is not affected by CSPGs in the normal brain ionic milieu. Both calcium and CSPGs are known to have many distinct roles in brain physiology, including brain repair, and our study suggests they may be functionally coupled through calcium diffusion properties.
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Affiliation(s)
- Sabina Hrabetová
- Department of Physiology and Neuroscience, NYU School of Medicine, 550 First Avenue, New York, NY 10016, USA
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